Field of the Invention
The present invention relates to an image forming apparatus. More particularly, the present invention relates to an image forming apparatus that includes conveyance paths separating at a branch point, and conveys sheets while switching sheet conveyance destinations at the branch point.
Description of the Related Art
Some image forming apparatuses have more than one conveyance path for sheets on which images are to be formed, and the conveyance paths separate from each other at a point. In some of such image forming apparatuses, a path switcher switches the conveyance destination of a sheet that has reached the branch point to one of the conveyance paths that separate at the branch point. The path switcher normally performs a switching operation to control a guide unit with a lever that is driven by a solenoid and a spring. By controlling the position and the posture of the guide unit through the switching operation, the path switcher can cause the sheet having reached the branch point to be conveyed through a conveyance path that is appropriately selected.
For example, JP 2005-239344 A discloses a path switcher that controls the rotational position of the guide unit that can be rotated about a supporting point with a lever that is rotated with a solenoid and a spring. In the path switcher according to JP 2005-239344 A, the lever for rotating the guide unit is formed with a first lever and a second lever, and applies force in such a direction that the first lever and the second lever move closer to each other. Further, a protruding portion of the guide unit is interposed between the first lever and the second lever. In the image forming apparatus according to JP 2005-239344 A, the rotational position of the guide unit is controlled by rotating the first lever and the second lever having the protruding portion of the guide unit interposed in between.
Meanwhile, an image forming apparatus is expected to have a higher operation speed these days. As the operation speed has increased, the conveyance velocity of each sheet being conveyed inside an image forming apparatus has become higher accordingly. In view of this, the guide unit of each path switcher is expected to perform a quicker switching operation. This is because a sheet cannot be conveyed to the downstream side of the branch point before the switching operation of the guide unit is completed.
However, a path switcher such as the above described conventional path switcher is designed to perform a switching operation in such a state where the protruding portion of the guide unit is interposed between the first lever and the second lever, and both the first lever and the second lever are in contact with the protruding portion of the guide unit. In a path switcher having such a structure, it is difficult for the guide unit to perform a quick switching operation.
During a switching operation, friction is generated between the protruding portion of the guide unit and the levers between which the protruding portion is interposed. The position for the levers to hold the protruding portion of the guide unit moves away from or moves toward the supporting points of the levers during a switching operation. The position for the levers to hold the protruding portion moves relative to the interposing surfaces of the levers between which the protruding portion is interposed.
In a path switcher having such a structure that the protruding portion of the guide unit is interposed between the levers from both sides, and is in contact with the interposing surfaces of both of the levers, a large frictional force is generated between the protruding portion of the guide unit and the interposing surfaces of the levers during a switching operation. As a result, the large frictional force between the protruding portion of the guide unit and the levers for holding the protruding portion during a switching operation turns into a high resistance to the spring and solenoid that apply the force necessary for the switching operation. As the resistance is high, the time required for the guide unit to complete the switching operation is long.